A semiconductor device, for example, a microwave amplification device, which are used with a high frequency band, composed of active elements, such as a field effect type transistor, passive elements, such as a resistance and a capacitor, and circuit elements, such as a microstrip line for transmitting a high frequency signal, and these circuit elements are formed for example, on a semi-insulating substrate. A ground conductor is formed on an opposite surface of the semi-insulating substrate. And, when grounding a circuit element, the circuit element provided on the semi-insulating substrate and the ground conductor formed on the back side of the semi-insulating substrate are electrically connected through a VIA (via) hole for passing through the semi-insulating substrate, for example.
The VIA-hole provides a through hole passed through from one surface to a surface of another side of the semi-insulating substrate, and is having structure which forms a conductive layer in an inner surface of the through hole. The through hole is formed, for example by etching, and the conductive layer is formed by plating, vacuum evaporation, etc.
The VIA-hole of a configuration described above has some which are described in the Patent Document 1 etc.
Patent Document 1: Japanese Patent Application Laid-Open Publication No. H02-288409.
As the conventional semiconductor device described above, the VIA-hole is formed, for example by etching, and the conductive layer formed in the inner surface of the VIA-hole is formed by methods, such as plating and vacuum evaporation.
However, when forming the conductive layer in the inner surface of the VIA-hole, the so-called “disconnection caused by step”, by which metal performing the plating or the vacuum evaporation is not fully formed and the conductive layer is not formed in a part of inner surface of the VIA-hole, may occur. As a result, grounding of the circuit element becomes insufficient and it becomes a cause by which the electrical characteristics of a microwave amplification device etc. deteriorate.
The object of the present invention is to provide a semiconductor device for solving the above-mentioned fault and preventing the disconnection caused by step of the VIA-hole, etc., and a fabrication method of the semiconductor device.